The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventor(s), to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Image and video compression are widely used in many applications. Compression methods are classified based on an amount of distortion between compressed data and the original source of the compressed data. Compression methods are typically classified as lossy, visually lossless, and lossless. Lossy compression has a high compression ratio but suffers from distortion due to information loss during compression. Lossless compression has virtually no information loss, but has a limited compression ratio. Visually lossless compression tolerates information loss that would not be evident to the human eye and therefore can manage a higher compression ratio than lossless compression. Visually lossless or lossless compression is required in fields that tolerate little or no information loss. For instance, lossless compression is often necessary for medical imaging. Applications that require a fixed low compression ratio and little information loss typically employ visually lossless compression.
Image and video processing systems store uncompressed images in memories for later processing. As image sizes grow, the increasing amount of memory required to store uncompressed images becomes unfeasible. Compression methods must balance the amount of storage necessary to store the data of an image with the data loss resulting from compression. When images are compressed, the image as a whole is often subject to the same compression ratio even though portions of the image may be more or less susceptible to compression. For example, portions of the image having a high frequency variation will suffer more data loss in compression than portions having a low frequency variation.